(CNN) -- Surrounded by FBI agents and US marshals, Bryan Denson's first encounter with an ex-CIA spy nicknamed "Batman" came in 2009 in a Portland, Oregon, courtroom.

But as Jim Nicholson faced the judge, Denson noticed the ex-spy's expression bore little of the hero-like confidence that earned him his nickname during his 26 years serving the US government.

Denson says in 1997, Nicholson became the highest-ranking CIA officer ever convicted of espionage, after selling the identities of hundreds of CIA trainees and troves of highly classified files to Russia's foreign spy service.

On this January day, though, Nicholson entered court to answer new charges: that he had not only reconnected with the Russians from inside prison, but had enlisted his son, Nathan Nicholson, to serve as his intermediary.

To read more from CNN, including a Q&A with Bryan and an exclusive excerpt from The Spy's' Son, click here.